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Control circuit protection / Isolation

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ivanr

Member
Location
Slough, United Kingdom
Occupation
Engineer
Hope this is the right forum for this.

I have a small control box housing a PLC and HMI.
Upstream of the PLC is the disconnect/isolator switch followed by UL489 MCB, followed by Control Isolating transformer, secondary feeding PLC and control circuit.

Would I be right in saying that I can use a UL508 Disconnect/Isolator (non-fused) instead of a UL98 disconnect which seems overkill as there are no power circuits in the control panel. Any thing else I should know.

FLA of the panel is only 2 Amps.
 
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drktmplr12

Senior Member
Location
South Florida
Occupation
Electrical Engineer

UL98 vs UL508

I have a question about installing a disconnect on the primaries to a transformer. I'm also going to put a contactor after the disconnect and before the transformer. I have another post going concerning the contactor. Due to space limitations, I'd really like to put the disconnect and contactor...
forums.mikeholt.com

read this, it might have your answer.
 
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ivanr

Member
Location
Slough, United Kingdom
Occupation
Engineer
This is the UL508 switch I was referring to:
Rs Comps (E14841)

I have seen the links above about UL98 vs UL508 but they tend to speak about power or motor circuits, I have none of these and I have only control circuitry in the control panel.
 
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